To the Editor

Abstract

We read with interest the article by Johnston et al. on “Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout strengths” [ [1] Johnston T.L. Karaikovic E.E. Lautenschlager E.P. Marcu D. Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout strengths. Spine J. 2006; 6: 667-672 Abstract Full Text Full Text PDF PubMed Scopus (176) Google Scholar ]. The results showed that cervical pedicle screw fixation had higher pullout strength and lower loosening rate at the bone-screw interface [ [1] Johnston T.L. Karaikovic E.E. Lautenschlager E.P. Marcu D. Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout strengths. Spine J. 2006; 6: 667-672 Abstract Full Text Full Text PDF PubMed Scopus (176) Google Scholar ]. We found the results not surprising; however, we believe the report should warn surgeons on the high risks with cervical pedicle screw placement [ 2 Kast E. Mohr K. Richter H.P. Borm W. Complications of transpedicular screw fixation in the cervical spine. Eur Spine J. 2006; 3: 327-334 Crossref Scopus (153) Google Scholar , 3 Ludwig S.C. Kramer D.L. Balderston R.A. Vaccaro A.R. Foley K.F. Albert T.J. Placement of pedicle screws in the human cadaveric cervical spine:comparative accuracy of three techniques. Spine. 2000; 25: 1655-1667 Crossref PubMed Scopus (219) Google Scholar , 4 Neo M. Sakamoto T. Fujibayashi S. Nakamura T. The clinical risk of vertebral artery injury from cervical pedicle screws inserted in degenerative vertebrae. Spine. 2005; 24: 2800-2805 Crossref Scopus (215) Google Scholar ]. Seybold et al. [ [5] Seybold E.A. Baker J.A. Crisciticello A.A. Ordway N.R. Park C.K. Connolly P.J. Characteristics of unicortical and bicortical lateral mass screws in the cervical spine. Spine. 1999; 22: 2397-2403 Crossref Scopus (74) Google Scholar ] showed years ago that unicortical lateral mass screw fixation has a much lower complication rate with pullout strength equivalent to bicortical lateral mass screws. Sekhon [ [6] Sekhon L.H. Posterior cervical lateral mass screw fixation:analysis of 1026 consecutive screws in 143 patients. J Spinal Disord Tech. 2005; 18: 297-303 Crossref PubMed Scopus (84) Google Scholar ] showed the high clinical success rate with very low complication rate in placement of lateral mass screws with over 1,000 screws placed without a neurovascular injury. There are numerous clinical and investigational reports describing the risks with cervical pedicle screw fixation [ 2 Kast E. Mohr K. Richter H.P. Borm W. Complications of transpedicular screw fixation in the cervical spine. Eur Spine J. 2006; 3: 327-334 Crossref Scopus (153) Google Scholar , 3 Ludwig S.C. Kramer D.L. Balderston R.A. Vaccaro A.R. Foley K.F. Albert T.J. Placement of pedicle screws in the human cadaveric cervical spine:comparative accuracy of three techniques. Spine. 2000; 25: 1655-1667 Crossref PubMed Scopus (219) Google Scholar , 4 Neo M. Sakamoto T. Fujibayashi S. Nakamura T. The clinical risk of vertebral artery injury from cervical pedicle screws inserted in degenerative vertebrae. Spine. 2005; 24: 2800-2805 Crossref Scopus (215) Google Scholar ]. Most recent, Kast et al. [ [2] Kast E. Mohr K. Richter H.P. Borm W. Complications of transpedicular screw fixation in the cervical spine. Eur Spine J. 2006; 3: 327-334 Crossref Scopus (153) Google Scholar ] showed only 70% of cervical pedicle screws were placed correctly. The authors went on to state that cervical pedicle screws should only be used by highly experienced spine surgeons and highly selected patients. Neo et al. [ [4] Neo M. Sakamoto T. Fujibayashi S. Nakamura T. The clinical risk of vertebral artery injury from cervical pedicle screws inserted in degenerative vertebrae. Spine. 2005; 24: 2800-2805 Crossref Scopus (215) Google Scholar ] also had similar findings with 29% of cervical pedicle screws violating the pedicle. The authors went on to state that the anatomic deviation among the placement of cervical pedicle screws was surprising and recommended refinement in their technique. Lastly, in comparing three techniques for placement of cervical pedicle screws, Ludwig et al. [ [3] Ludwig S.C. Kramer D.L. Balderston R.A. Vaccaro A.R. Foley K.F. Albert T.J. Placement of pedicle screws in the human cadaveric cervical spine:comparative accuracy of three techniques. Spine. 2000; 25: 1655-1667 Crossref PubMed Scopus (219) Google Scholar ] concluded that although cadaver studies have provided guidelines for transpedicular screw placement, sufficient variation exists to preclude safe instrumentation. We would like to offer a closing comment in regard to placement of cervical pedicle screws. Although we place cervical pedicle screws in a select patient population, the prevention of serious injury is the key in placement of posterior fixation with either lateral mass or pedicle screws. Assuming surgeons will always obtain preoperative axial computed tomography scans to assess the foramen transversarium, we then recommend placing right-side fixation first. The left vertebral artery is dominant in the vast majority of the population; thus, should a vascular injury occur during fixation, it will likely initially be on the nondominant vertebral artery and hopefully less complicated. This recommendation will allow the surgeon to manage the complication and alter the surgery accordingly [ 7 Epstein N.E. From the neurointerventional lab…intraoperative cervical vertebral artery injury treated by tamponade and endovascular coiling. Spine J. 2003; 3: 404-405 Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar , 8 Dickerman R.D. Reynolds A.S. Morgan B.C. Posterior decompression and fusion: dorsal migration of the spinal cord is the key!. J Clin Neurosci. 2007; 14: 185-186 Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar ]. We congratulate Johnston et al. [ [1] Johnston T.L. Karaikovic E.E. Lautenschlager E.P. Marcu D. Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout strengths. Spine J. 2006; 6: 667-672 Abstract Full Text Full Text PDF PubMed Scopus (176) Google Scholar ] on their contribution to cervical spine biomechanics and only offer these comments to enlighten the surgical community on the high anatomic variance on cervical pedicles and subsequent risks associated with cervical pedicle screw placement.